One of the frequent problems encountered with synthetic polymers is instability on exposure to light, heat and atmospheric conditions, leading to deterioration and color change. Over the years industry has developed many additives that are blended into the polymer to alleviate the problem and is still continuously searching for new materials that will prolong the life of the polymeric product. In addition to the above harmful conditions, many polymers contain metal catalyst residues that can exert adverse effects on the synthetic polymer fiber, film or other article.
The user of additives, collectively called stabilizers, to prevent or inhibit degradation of natural and synthetic materials is known. It is also known that a compound that stabilizes against heat and/or oxygen degradation in a material may not stabilize against light degradation in the same material, and vice versa. It is further known that a compound which exerts some form of stabilization in one type of synthetic or natural material may be completely ineffective in another type of material. Thus, compounds are classified as antioxidants, light stabilizers, heat stabilizers, etc., depending upon the stabilizing effect a particular compound may have on a specific material or type of material. As a consequence, in many cases mixtures of stabilizers are used to obtain desired protection against one or more forms of degradation.
It has now been found that a novel class of polysiloxanes having pendant sterically hindered phenol moieties can be produced that stabilize synthetic polymers against the deleterious effect caused by exposure to atmospheric conditions.
Polysiloxanes containing t-butyl substituted phenyl groups have been known for many years. Thus, U.S. Pat. No. 3,328,350, issued June 27, 1967 to G. M. Omietanski et al., discloses polysiloxanes of superior stability towards oxidative degradation which are the reaction products of selected substituted phenols with acyloxy terminated polysiloxanes. The final product contains the phenyl group in the polymer chain and it is not a pendant group.
In U.S. Pat. No. 3,328,450, issued June 27, 1967 to E. P. Plueddemann, there are disclosed alkyl phenol-substituted organosilicon compounds and polysiloxanes containing such compounds. However, none of the compounds disclosed contain a pendant sterically hindered phenol moiety connected to the silicon atom via a carbonyloxy-containing link.
The disclosure in U.S. Pat. No. 3,579,467, issued May 18, 1971 to E. D. Brown, also disclosed polysiloxanes containing a phenol moiety. However, the phenol moiety is not connected to the silicon atom via a carbonyloxy-containing link.
In U.S. Pat. No. 4,430,235, issued Feb. 7, 1984 to N. S. Chu et al., polymeric siloxane antioxidants are disclosed that contain an antioxidant moiety, for example, a hindered phenolic group. However, the reference does not suggest or disclose any compound in which the phenolic moiety is connected to the silicon atom via a carbonyloxy-containing link.
U.S. Pat. No. 4,535,113, issued Aug. 13, 1985 to G. N. Foster, et al., discloses olefin polymer compositions containing silicone additives. The siloxane additives, however, are not those of the instant invention.
The invention described in U.S. Pat. No. 4,645,844, issued Feb. 24, 1987 to A. Berger et al., discloses phenoxy-containing silane compounds wherein the phenoxy group is attached to the silicon atom via a methylene or alkylene link and nowhere suggests or discloses a connection via a carbonyloxy-containing link.
A number of abstracts in CA Selects Organosilicon Chemistry disclose a variety of phenol-substituted silanes useful as antioxidants, however, none of them disclose or suggest the compounds of this invention. (See: the silane of Issue 8, 1986, page 14, abstract 131201e; the disiloxane of Issue 9, 1986, page 21, abstract 15060g; the disiloxane of Issue 10, 1986, page 10, abstract 169116u; the silane of Issue 14, 1986, page 11, abstract 739b; and the silane of Issue 17, 1986, page 12, abstract 61488y.)